The influence of thermal treatment on microstructure and functional properties of Fe89.8Ni1.5Si5.2B3C0.5 amorphous alloy and their mutual correlations were studied. Structural transformations were identified using DSC and characterized using X-ray diffraction. The alloy was found to exhibit a wide supercooled liquid region before crystallization, while kinetic parameters of observed structural transformation indicated high complexity of these processes, involving simultaneous movement of large groups of atoms. Investigation of magnetic and electrical properties of the alloy showed that structural relaxation prior to crystallization affected both magnetic susceptibility and electrical resistivity of the alloy, leading to an increase in both, which can be correlated to a decrease in number of defects and an increase in free volume in the alloy sample, enabling greater mobility of magnetic domain walls, but also decreasing electron density of states at the Fermi level. (C) 2013 Elsevier B.V. All rights reserved.